This invention relates to apparatus for continuously pushing out a sheet product from a sheet blank in which cut lines defining the sheet products are formed in advance.
Sheet products such as cards, labels, tags, etc. made of paper, cardboard or synthetic resin, and such as profiled two-dimensional sheets of cardboard from which three-dimensional articles such as boxes are fabricated, are produced on a mass-production basis by punching them out from a sheet blank. For this purpose, a cutting die having the same contour as the profile of the sheet products is used for punching out the sheet products in one action. Alternatively, the cutting die is used to form in the sheet blank cut lines corresponding to the contour of the sheet products in advance. In this case, the sheet blank cut beforehand with the cut lines must be subjected to a secondary process in which the part of the blank surrounded by the cut lines is pushed out or separated from the remaining part of the blank. Among these two methods, the latter is more often used in industry.
The secondary process of the latter method may be carried out with the sheet blank precut with cut lines held stationary. But more advantageously, the process is carried out while the sheet blank is moved or conveyed continuously. This enables the process to be incorporated in a continuous production line in which other automatic production processes are carried out.
Conventional apparatus for carrying out the above mentioned secondary process comprises a pair of cylindrical or barrel-shaped drums disposed one above the other and having pushing-out pins or the like implanted on the outer surfaces thereof. A sheet blank to be subjected to the pushing-out process is successively fed into the space between the drums while these drums are being rotated in opposite directions, whereby the part of each sheet blank defined by the cut lines is successively pushed out by the pushing-out pins.
In this apparatus, however, undue forces are imposed on each sheet blank because of difference in peripheral speed between the tip parts and proximal parts of the pushing-out pins and because of continual change of the angular position of the pushing-out pins from the instant immediately prior to the pushing-out operation to the instant immediately after the same. This problem cannot be solved even when the diameter of the drums is increased. Moreover, in this type of the apparatus, sheet products and scrap blanks from which the sheet products are separated tend to be caught by the pins on the drums which are not associated therewith.